Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$42.29	5.261%	$44.5149	$44.51	$44.50	$44.50
Purchase #2	$13.27	4.581%	$13.8779	$13.88	$13.90	$13.90
Purchase #3	$17.53	3.748%	$18.187	$18.19	$18.20	$18.20
Purchase #4	$40.83	4.266%	$42.5718	$42.57	$42.55	$42.60
Purchase #5	$57.73	5.814%	$61.0864	$61.09	$61.10	$61.10
Purchase #6	$16.74	7.622%	$18.0159	$18.02	$18.00	$18.00
Purchase #7	$60.71	6.179%	$64.4613	$64.46	$64.45	$64.50
7 purchase totals =	$249.10		$262.7152	$262.72	$262.70	$262.80